THE BLAST FURNACE. ••'...-" • 41
necessary to keep this fact in mind in considering the1 results obtained in Western Germany from ores running under 35 per cent. in iron.
• Bed hematite is the most desirable of all iron ores. Most of the Bake'Superior deposits are of this variety, and they alone supply as'much ore as comes from any other one country, while the. Bilbao region in Spain, the Minette district of Lothringen and Luxemburg, the West Coast of England and the beds of Alabama, all mine the same mineral and are of world-wide importance. Of lesser interest are the deposits in the basin of the Don in Southern Eussia, the southeast coast of Cuba, the Tafna beds in Algeria and the Bell Island mines in Newfoundland.
(2) Carbonate (FeCOs), called also spathic ore, black band, clay iron stone, etc., contains 48.3 per cent, of iron. Very little is used in the United States, but it is the basis of the great Cleveland; district near Middlesborough, England, and of -the iron industry of Bohemia and Styria, and is produced in large quantities in Hungary and Spain. In former days the Spanish mines rejected this ore as inferior, but it is now mined extensively. Almost everywhere spathic ore is roasted. The kilns are such as are used for limestone, and sometimes coal is mixed with the ore, while at other places tunnel head gases are used for fuel. The fuel needed is less than might be supposed, from 75 to 100 pounds of coal per ten'of ore being the usual practice, because the expulsion of the carbonic acid leaves the iron in the form of FeO, and this burns to Fe203, so that for every ton of raw ore the burning of the iron produces an amount of heat equal to what would be produced by 35 pounds of coal.
. (3) Magnetite (Fe304) contains 72.41 per cent, of iron. It is strongly attracted' by the magnet, while other iron ores are only slightly influenced by strong currents. It is currently believed that more fuel is required for smelting magnetite than for hematite, but recent results with Swedish magnetic ores in German and Austrian furnaces indicate that the difficulties may have been overrated.: Magnetite is found in enormous quantities in central and northern Sweden and in the northeastern part of the United States. In both countries there are some rich beds, and some of great extent that are lean in iron. Within the last few years great strides 'have been made: in the'concentration of these ores, both in Sweden and